Adam collecting Aphyllon cooperi in the
Extant distributions of plants and plant communities are result of millions of years of interplay between ecological and evolutionary forces. Why are some lineages species-rich but with small ranges, while others consist of only a few widespread species? Many species persist only in very narrow geographic localities or ecological conditions, yet over long periods of time are not dispersal limited. What are the evolutionary processes that give rise to such rich and varied biodiversity? My research uses a specimen-based, phylogenomic approach to understand the evolutionary factors that contribute to plant endemism.
I circumscribe “endemism” broadly, including biogeographical endemism of range-restricted taxa, edaphic endemism, and phylogenetic endemism; however, much of my research is focused on host endemism in parasitic plants, and the associated genomic consequences of this life-history strategy.
I have been working at the UC and Jepson herbaria since beginning my Ph.D. in 2012. A complete CV can be found here. (last updated Nov. 2016)
Host endemism— My major research focus is using the clade of New World Orobanche to understand the role of host-specificity as a driver of diversity in holoparasites. Using molecular phylogenetics, I identified numerous cryptic host-specific lineages, previously unrecognized due to the reduced morphology. Herbarium and field studies to better characterize and describe these lineages are in progress.
Parasitic plant genomics— In addition to macroevolutionary consequences of parasitism, a major aim of my research is understanding genomic evolution of parasitic plants. As part of my NSF DDIG-funded research, I am using genome skimming to test recently proposed models of gene loss across the phylogeny. Does it happen gradually over time, or is it episodic and variable across lineages? What is the tempo and mode of gene loss and diversification? In the future, targeted sequence capture could be used to investigate the evolution of genes suspected to play a role in parasitism. Looking across a phylogeny to compare species (or populations) on different hosts may revel particular loci with high levels of divergence, or signatures of a selective sweep. Are the same genes consistently involved in adaptation to a new host, or are there many possible pathways? One unexpected outcome of this study has been strong evidence for host-to-parasite horizontal gene transfer of the coding gene rbcL in an undescribed species, revealing that parasitism can also be a driver of increased genetic variation.
Comparative studies— Parasitism has evolved at least 12 times among angiosperms. By studying several clades of parasites, we can understand each of them better, as well as the underlying eco-evolutionary processes. As part of my NSF-DDIG I have begun a collaboration to develop dwarf mistletoes (Arceuthobium) as a parallel study system.
Edaphic endemism— In parasitic plants, the host is the dominant substrate, but autotrophic plants the substrates are usually abiotic. As part of my doctoral dissertation I designed a comparative phylogenetic study using both hypothesis-testing and model-selection methods that found that earlier flowering of plants on serpentine soils compared to nearby plants on other soils is more likely the result of ecological filtering or exaptation than post-colonization selection for earlier flowering time.
Diversification of Hesperolinon— One lineage with substantial diversity on serpentine soils is the western flax genus Hesperolinon, endemic to the western United States. It is notable for its high and geographically concentrated species richness on serpentine-derived soils, with 12 of the 13 species found in Lake and Napa Counties of California, an area smaller than the state of Delaware. Most diversification in Hesperolinon has taken place in the last 1-2 million years, coincident with the uplift of California’s Coast Range and the expansion of available habitat. What else can such radiations tell us about the processes of diversification of edaphically harsh substrates?
Curatorial internship in the Galapagos— In the summer of 2011 I worked as a curatorial assistant/intern at the Charles Darwin Research Station Herbarium.
See my complete CV here (updated Nov. 2016). Reprints of papers available upon request
I believe teaching and research are mutually beneficial. I am passionate about teaching, both in the classroom and through research experiences. I am committed to improving my own pedagogical skills through workshops, classrooms, and course evaluations. To that end, I have completed a Certificate of Teaching and Learning in Higher Education offered by the UC Berkeley Graduate Division. In the classroom, I have experience designing and teaching laboratory, field, and discussion sections for a variety of classes including Vascular Plant Systematics, Medical Ethnobotany, California Plant Life, and Climate Change and the Future of California. I have also assisted with several public workshops offered by the Jepson Herbarium and other outreach programs.
Engagement in scholarship and undergraduate research is the highest realization of student learning. I am currently working with one honor’s thesis student, and two other undergraduates through the Undergraduate Research Apprentice Program (URAP). Previous students have presented their work at regional conferences. If you are interested in working with me, please send me an email.
One of the best parts of being a field botanist is the opportunity to work in beautiful natural areas. I enjoy virtually anything that will get me outside: biking, hiking, backpacking, cross-country skiing, paddle sports, conservation work projects and gardening. I also enjoy cooking, do-it-yourself projects, and contemplating the interplay between science and religion historically, and in modern society. Since moving out to California I have also taken up homebrewing.
Before moving to California, I worked briefly as a professional canoe guide in the Boundary Waters of northern Minnesota. I taught wilderness camping, canoeing, natural history, and leadership skills to a diverse array of people, but mostly middle and high schoolers. I’m always looking forward to my next trip to the northwoods.